Anti-diabetic potential of selected Malaysian seaweeds

The emergence of type 2 diabetes mellitus (T2DM) as the pre-eminent global non-infectious disease has driven the search for new anti-diabetic strategies including utilising traditional food and herbs. In this investigation, we describe the anti-diabetic potential of six selected Malaysian seaweed species against recognised pharmacological targets. Specifically, we measured their ability to inhibit α-glucosidase and dipeptidyl-peptidase-4 (DPP-4) and also their ability to stimulate incretin hormone secretion in vitro. Crude water extracts of Halimeda macroloba, Padina sulcata, Sargassum binderi and Turbinaria conoides possessed potent inhibitory activities against α-glucosidase and DPP-4. The highest inhibitory activity against α-glucosidase was found in water extracts of the green seaweed species H. macroloba with an IC₅₀value of 6.388 mg mL⁻¹. Crude water extracts of the brown seaweeds studied namely P. sulcata, S. binderi and T. conoides, exhibited potent DPP-4 inhibition compared with the green seaweed H. macroloba. The brown seaweed also stimulates secretion of glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) from pGIP neo STC-1 cells in vitro. H. macroloba stimulated GLP-1 secretion but not secretion of GIP.